The present disclosure is directed to an engine management system for an internal combustion engine. In particular, this disclosure is directed to providing a system that allows an operator to transfer engine management data between a palm-size computer and an engine control system, and to transfer engine management files between the palm-size computer and an external computer. As an example, a system according to one embodiment enables an operator to calibrate the engine operation, either while the engine is not running or while operating in its intended environment, by changing trim control values, which represent modifications to base engine control values that are based on an engine control map. More particularly, a recreational vehicle rider can generate trim control maps for calibrating base engine control maps, e.g., such as for ignition timing and fuel delivery, while riding or driving the vehicle.
It is believed that the performance of an internal combustion engine is dependent on a number of factors including the operating cycle (e.g., two-stroke, four-stroke, Otto, diesel, or Wankel), the number and design of combustion chambers, the selection and control of ignition and fuel delivery systems, and the ambient conditions in which the engine operates.
Examples of design choices for a combustion chamber are believed to include choosing a compression ratio and choosing the numbers of intake and exhaust valves associated with each chamber. In general, it is believed that these choices cannot be changed so as to calibrate engine operation after the engine has been built.
With regard to ignition systems, breaker point systems and electronic ignition systems are known. It is believed that these known systems provide spark timing based on an operating characteristic of the engine, e.g., speed of rotation and load. In the case of breaker point systems, it is believed that engine speed is frequently detected mechanically using centrifugally displaced weights, and that intake manifold vacuum is commonly used to detect engine load. In the case of electronic ignition systems, it is believed that engine speed is generally detected with an angular motion sensor associated with rotation of the crankshaft, and that engine load is frequently detected, for example, by the output of a throttle position sensor. In each case, spark timing is believed to be fixed according to these known systems for a given operating state of the engine.
With regard to fuel delivery systems, carburetors and fuel injection systems are known. It is believed that these known systems supply a quantity of fuel, e.g., gasoline, that is based on the amount of air being admitted to the engine, i.e., in accordance with the position of the throttle as set by the operator. In the case of carburetors, it is believed that fuel is delivered by a system of orifices, known as xe2x80x9cjets.xe2x80x9d As examples of carburetor operation, it is believed that an idle jet may supply fuel downstream of the throttle valve at engine idling speeds, and that fuel delivery may be boosted by an accelerator pump to facilitate rapid increases in engine speed. It is believed that most carburetors must be disassembled and different size jets or pumps installed to modify the amount of fuel delivery. However, this is a laborious process that, it is believed, that most often, can only be done while the engine is not running.
It is believed that known fuel injection systems, which can be operated electronically, spray a precisely metered amount of fuel into the intake system or directly into the combustion cylinder. The fuel quantity is believed to be determined by a controller based on the state of the engine and a data table known as a xe2x80x9cmapxe2x80x9d or xe2x80x9clook-up table.xe2x80x9d It is believed that the map includes a collection of possible values or xe2x80x9csetpointsxe2x80x9d for each of at least one independent variable (i.e., a characteristic of the state of the engine), which can be measured by a sensor connected to the controller, and a collection of corresponding control values, for a dependent variable control function, e.g., fuel quantity.
Conventionally, it is believed that maps are developed by the engine manufacturer and permanently set in an engine control unit at the factory. Currently, for on-road vehicles, this is believed to be legally required in order to meet emissions regulations. However, it is believed that even when it is not legally required, the manufacturers prevent engine operators from modifying the maps for a variety of reasons such as the manufacturers believe that their maps provide the best engine performance, the manufacturers are afraid that an engine operator might damage the engine by specifying inappropriate control values, or the manufacturers assume that an engine operator might not have sufficient skill to properly modify a map. However, it is believed that the manufacturers have xe2x80x9coptimizedxe2x80x9d their maps to perform best under a set of conditions that they specify. In most cases, it is believed that these conditions do not match the conditions in which the engine is operated. Consequently, stock maps are believed to limit, rather than optimize, an engine""s performance.
It is further believed that ambient conditions such as air temperature, altitude, and barometric pressure affect engine performance. It is believed that these conditions generally impact the entire operating range of the engine. In the case of fuel injection, it is believed to be known to compensation for these conditions by calculating an adjustment for every operating state of the engine.
Thus, engine performance is believed to be substantially dependent on how combustion is accomplished in the ambient conditions. The stoichiometric ratio of air to gasoline is 14.7:1. However, it is believed that ratios from about 10:1 to about 20:1 will combust, and that it is often desirable to adjust the air-fuel ratio to achieve specific engine performance (e.g., a certain level of power output, better fuel economy, or reduced emissions). Similarly, it is also believed to be desirable to adjust ignition timing, commonly measured in degrees of crank rotation before a piston reaches top-dead-center of the compression stroke, to achieve specific engine performance (e.g., lowest fuel consumption or reduced emissions).
It is believed to be a disadvantage of known ignition timing systems and fuel delivery systems that engine operation is constrained by the fixed controls established by the suppliers of these systems. It is also believed to be a disadvantage that any possible adjustments to these known systems requires a technician to reconfigure one or more of the system components, or to disassemble the system, install substitute components, and reassemble the system. Therefore, it is further believed to be a disadvantage of these known systems that neither the effectiveness nor the sufficiency of these adjustments can be determined while continuously operating the engine in its intended environment. And it is yet further believed to be a disadvantage of these known systems that the effect of these adjustments cannot be directly compared.
There is believed to be a need to overcome these disadvantages of known ignition and fuel delivery systems.
The present invention provides an engine management system for an internal combustion engine. The engine management system comprises an engine control system calculating an engine operating control value, a palm-size computer transportable relative to the engine control system, and an external computer communicating with the palm-size computer. The engine operating control value is adapted to be supplied to the internal combustion engine to vary engine performance. The palm-size computer has height, width, and thickness dimensions that are no larger than approximately 6 inches by approximately 4 inches by approximately 1 inch. The palm-size computer runs a set of engine management tools that communicate engine management data to the engine control system. The external computer downloads to the palm-size computer engine management tools and engine management files, and uploads from the palm-size computer engine management files.